Overvoltage and electronic relay circuit for capacitor discharge ignition systems

ABSTRACT

An energy pulsing circuit is provided for applying energy pulses to an ignition coil in synchronization with external switching means such as the breaker-points of an automobile. A power switching circuit is connected between the energy pulsing circuit and an external power source to apply operating potential to the ignition system involved under normal voltage conditions, and to automatically disconnect power to the ignition system upon sensing abnormal voltage conditions. A voltage abnormality sensing circuit is provided to render the power switching circuit non-conductive in response either to an overvoltage applied to the circuit or to a reduced residual feedback voltage which may occur at the ignition switch upon opening the switch when the engine is running.

United States Patent 1191 Schuette. et a1.

1451 Aug. 13, 1974 OVERVOLTAGE AND ELECTRDNKC RELAY CIRCUIT FOR CAPACE'E'QR DISCHARGE IGNITION SYSTEMS lnventors: Gunter G. Schuette, Addison;

William J. Warner, Schaumburg, both of 111.

Assignee: Motorola, 1nc., Franklin Park, 111.

Filed: Oct. 28, 1971 Appl. No.: 193,601

Related US. Application Data Continuation of Ser. No. 1,597, Jan. abandoned.

US. 01. 123/148 ocu, 123/148 E 1111. c1. F02p 1/00 Field 01 Search 123/148 12 References Cited UNITED STATES PATENTS Weiss 123/148 Riff 310/81 Oishi 321/2 32 Eseuurroni Leftwich 123/148 11/1971 Dogadko 123/148 l/1972 Schuette 123/148 Primary Examinerl..aurence M. Goodridge Assistant Examiner--Ronald B. Cox Attorney, Agent, or Firm-James W. Gillman 5 7] ABSTRACT An energy pulsing circuit is provided for applying energy pulses to an ignition coil in synchronization with external switching means such as the breaker-points of an automobile. A power switching circuit is connected between the energy pulsing circuit and an external power source to apply operating potential to the ignition system involved under normal voltage conditions, and to automatically disconnect power to the ignition system upon sensing abnormal voltage conditions. A

voltage abnormality sensing circuit is provided to render the power switching circuit non-conductive in response either to an overvoltage applied to the circuit or to a reduced residual feedback voltage which may occur at the ignition switch upon opening the switch when the engine is running.

12 Claims, 1 Drawing Figure PAIENTED 31974 INVENTORS- GUNTER G. SCHUETTE WILLIAM J. WARNER BY M ad M NH oIhNN ATTORNEYS.

BACKGROUND OF THE INVENTION This invention relates generally to ignition systems of the type-providing a high voltage, low current energy pulse to the primary winding of an ignition coil, and more particularly to an improved capacitor discharge ignition system.

Although the invention herein disclosed has particular utility when used in combination with capacitor discharge ignition systems, it should be understood that the power switching circuit of this invention can be used with other types of electronic ignition systems.

.Capacitor discharge ignition systems, i.e., systems which utilize a capacitor for intermittently discharging a relatively high voltage energy pulse through an ignition coil, have found relatively widespread and popular use in connection with internal combustion engines.

Such capacitor discharge ignition systems have several advantages over conventional Kettering ignition systems. One of the advantages that is obtained is that the power drain from the automobile battery is substantially reduced when using a capacitor discharge ignition system. Another advantage of capacitor discharge ignition system is that a spark of higher voltage, i.e., higher fuel igniting properties, can be generated more readily with a somewhat run down storage battery connected thereto, than could otherwise be obtained by a conventional ignition system. Yet another advantage obtained from capacitor discharge ignition systems is that the spark potential generated at spaced-apart electrodes within a spark plug remains substantially constant over a much wider range of engine speeds than otherwise can be obtained from the conventional ignition system.

Despite the advantages mentioned hereinabove, as well as others not mentioned, capacitor discharge ignition systems of the prior art, as well as other types of ignition systems, are readily damaged whenever an overvoltage is applied to the ignition system. For example, if for some reason the connection of the automobile battery becomes loose or is removed while the engine is running, a high voltage, in the order of 30 volts or more, is supplied from the alternator through the ignition circuit of the automobile, as well as through some of the accessories connected to the ignition switch and will damage the ignition system. That is, this voltage, as compared to the usual 12 volts, is sufficiently high to destroy some or all of the electronic components which go into forming the capacitor discharge ignition system. One attempt by the prior art to circumvent this serious problem is to provide a manually operated switch which, when actuated, will discon-- nect the capacitor discharge ignition system from the ignition coil of the automobile and reconnect the conventional ignition system. This at least allows the operator of the automobile to continue on his journey. Another approach by the prior art is to bypass some or all of the active electronic components such as transistors or the like with voltage protection devices such as Zener diodes. Although this approach does the job to some extent it increases the cost of such ignition systems by increasing the number of components used in its circuitry.

Still another serious problem of prior art capacitor discharge ignition systems is that of the alternator residual feedback voltage, which when applied to the ignition switch, on the open side thereof, is sufficiently high to generate spark producing potentials at the output of the ignition system even after the ignition switch of the automobile has been turned off, i.e., switched to the open circuit condition. Since capacitor discharge ignition systems are relatively efficient, requiring only a small amount of current input to produce a high voltage spark discharge, the low voltage residual feedback from the alternator could maintain the automobile engine in a running condition after the ignition switch has been turned off.

SUMMARY OF THE lNVENTlON lt is therefore an object of this invention to provide an ignition system which will automatically be protected from the application thereto of overvoltages in excess of a predetermined voltage value.

Another object of this invention is to provide an ignition system which is rendered inoperative substantially instantaneously upon the opening of the ignition switch of an automobile.

Briefly, the ignition system of the illustrated embodiment includes an energy storage capacitor for receiving and storing a relatively high voltage energy pulse. The stored energy is then synchronously discharged from the storage capacitor, as for example by means of opening the breaker-points of the automobile, and applied to the primary winding of an ignition coil through a current control device such as a silicon controlled rectitier. Preferably, the energy pulse applied to the storage capacitor is developed in the secondary winding of a step-up transformer, the primary winding or windings thereof being connected to a transistor and in combination therewith form a single swing blocking oscillator. A trigger amplifier stage may be coupled to the secondary winding of the transformer to initiate conduction of the transistor of the blocking oscillator to apply a single energy pulse to the storage capacitor. Suitable.

regenerative feedback circuit means are provided between the output of the transistor of the blocking oscillator and its base electrode to drive the transistor rapidly to a current saturated condition. Upon completion of the saturated condition of the transistor, a reverse voltage feedback will occur in one of the primary windings of the transformer to render the transistor nonconductive. Regardless of the time duration between spark discharges, the transistor remains nonconductive until the next spark discharge occurs whereupon the single swing blocking oscillator formed by the transistor and its associated transformer will again deliver an energy pulse to the storage capacitor. Although the illustrated embodiment uses a single swing blocking oscillator to apply energy pulses to the storage capacitor it will be understood that any suitable energy pulsing circuit can be used.

Most advantageously, a power switching circuit is connected between the energy pulsing circuit and an external power source, such as the battery of an automobile. The power switching circuit includes a power switching current control device having load electrodes and a control electrode, one of the load electrodes being connected to the energy pulsing circuit and the other of the load electrodes arranged for connection to the external power source. A voltage abnormality sensing circuit is coupled to the control electrode of the current control device. The voltage abnormality sensing circuit has a circuit portion thereof connected to the accessory side of the ignition switch of the automobile for sensing the voltage values applied thereto with the ignition switch either in the open circuit or closed circuit condition. A second current control device is connected between the control electrode of the power switching current control device and ground potential and is maintained in a high resistance current blocking condition when normal operating potentials are applied to the power switching circuit and with the ignition switch in the on position. However, if an overvoltage occurs during operation, the second current control device is rendered highly conductive to provide a shunt current path for the control electrode of the power switching current control device to render it inoperative. Also, when the ignition switch is actuated to the off position, any residual feedback voltage which may occur on the open circuit side herein referred to as the accessory side of the switch will provide a voltage difference, when compared with the voltage of the battery, also to render the second current control device highly conductive to provide a shunt current path for the gate electrode of the power switching current control device to render it non-conductive. Therefore, an abnormal voltage condition of either an overvoltage, or a residual feedback voltage to the open side of the ignition switch, will instantaneously and automatically disconnect power from the ignition system.

By providing means for automatically disconnecting overvoltage potentials from the ignition system, the use of reference voltage devices connected in circuit with the various active circuit components of the ignition system is eliminated since overvoltage potentials never reach the ignition system. Also by providing means for sensing the difference of potential across the ignition switch of an automobile when in its open circuit condition, power can be positively removed from the ignition system to ensure positive turn-off of the automobile engme.

DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a schematic wiring diagram of the illustrated embodiment wherein the power switching circuit of this invention may be used.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing an ignition system designated generally by reference numeral includes an energy pulsing circuit 12 for applying energy to a storage element, such as a capacitor or to a primary winding of an ignition coil, to cause a spark producing energy pulses in a primary winding 14a of an ignition coil 14 which has a secondary winding 14b thereof readily connectable to any suitable spark utilization means such as the distributor of an automobile engine. The energy pulsing circuit 12 most advantageously is connected to a power switching circuit 16 which has a circuit point 18 thereof arranged for connection to an external power source 20 via a line 21. Preferably, the power source 20 is the battery of an automobile when the ignition system 10 is useful to control spark discharge at the spark plugs of the internal combustion engine of the automobile.

A switch 22 has one end thereof connected to line 21 for applying power to a circuit point 24 on the other side of switch 22 when the switch is actuated to its closed circuit condition. The switch 22 is here illustrated as the ignition switch of an automobile and functions in the well known manner. That is, closing of switch 22 also applies battery power to a plurality of accessory devices such as light bulbs, fan motors radio, etc., and the accessories are illustrated as a single group designated by reference number 26. Closure of switch 22 also energizes the power switching circuit 16 to apply operating potential to a circuit point 28 from which the energy pulsing circuit 12 receives its operating voltage. However, in accordance with this invention, operating potential is applied to circuit point 28 only when a normal voltage condition exists at circuit points 18 and 24 and will be instantaneously and permanently removed from circuit point 28 upon sensing either an abnormally high voltage at circuit point 18 or upon sensing a voltage difference between circuit points 18 and 24, and upon re-establishing of the normal voltage on circuit point 18 and 24, the power switching circuit 16 automatically applies power to circuit point 28.

During normal operating conditions, the potential at circuit point 24 is that provided by the power source 20 or, when the engine of the automobile is running, a slightly increased voltage as produced by an alternator 30 and a voltage regulator 32 which are also connected to circuit point 24, directly or indirectly, through various accessory wiring as is well known in the arts. The normal regulated voltage output as applied to circuit point 24 is in the order of 13 to 15 volts and also serves to charge the battery 20 when the engine is running. The regulated voltage output of alternator 30 is applied to battery 20 by means of a protection diode 34 which is forward biased when the voltage at the alternator 30 is more positive than the voltage at the battery 20 so as to forward bias the diode 34. However, upon reduction of the voltage at alternator 30, for example by shutting off the engine, reverse current flow from the battery 20 to the alternator 30 is prevented by the blocking condition of diode 34.

Because of the interconnection between alternator 30 and circuit point 24 either directly or indirectly, through various ones of a multitude of accessory devices, as indicated by reference numeral 26, a residual feedback voltage produced by the alternator 30 could and oftentimes does, appear at circuit point 24 after the ignition switch 20 is turned to the off position to stop the engine. However, because of the high efficiency of the energy pulsing circuit 12 only a small amount of current given at a reduced voltage is necessary to maintain the energy pulsing circuit 12 in an operating condition. This is particularly true in the case of a capacitor discharge ignition system as illustrated herein. Therefore, upon opening the ignition switch 22 the residual feedback voltage from alternator 30 as applied to circuit point 24, would maintain the engine in a running state.

A pulsing circuit 36 has one end thereof connected to circuit point 24 via a line 38 and the other end thereof intermittently connected to ground potential via an external breaker-point assembly 40 which may be located within the ignition distributor of the automobile engine. However, it will be understood that any suitable external pulse signal information can be used in place of the mechanical breaker-point assembly 40, as for example, a magnetic pulse output or a light signal output generated in synchronism with an internal combustion engine.

The energy pulsing circuit 12 includes a transistor 42 which has the collector electrode thereof connected to circuit point 28 and the emitter electrode thereof connected to a pair of primary windings 44a and 44b of a pulse forming step-up transformer 44. The primary winding 44a has the other end thereof connected to a temperature responsive resistor 46 through a parallel network comprising a resistor 48 and a diode 50. This circuit provides a regenerative feedback loop to the base electrode of transistor 42 to cause the transistor 42 rapidly to achieve a saturated current condition. Upon complete saturation, or substantially complete saturation, of transistor 42 a reduction in the rate of change of current in primary windings 44a and 44b provides a reversal of polarity within the winding 44a quickly to render transistor 42 to its current cut-off condition, which condition remains until a starting pulse is again applied to the circuit. Therefore, transistor 42 together with its associated components form a single swing, blocking oscillator which generates a stepup voltage in the secondary winding 440 of the transformer 44 and applies this increased voltage to an energy storage capacitor 52. Only a positive pulse of energy can be stored in capacitor 52 because of the series connected diode 54, which blocks current flow in one direction allowing capacitor 52 to become and remain charged, and which conducts current flow in the other direction to storage capacitor 52.

The energy stored in capacitor 52 is then applied to the primary winding 14a of the ignition coil 14 through a switching circuit herein illustrated as including a silicon controlled rectifier 56 which has its anode connected to capacitor 52 and its cathode connected to a circuit point 58 which, in turn, is arranged for connection to the primary winding 14a of the ignition coil 14. A diode 60 is connected in series with the diode 54 at the junction of capacitor 52 and provides a current path to ground potential for the secondary winding 440 of the transformer 44 for voltages of a given polarity, thus dampening any ringing effect within the closed loop formed by winding 44c, capacitor 52, and diode 54 within a relatively short period of time after the capacitor 52 is discharged.

The pulsing circuit 36 includes a pulse forming transformer 62 which has a primary winding 62a connected to circuit point 24 through a resistor 64 and to the mechanical breaker-point assembly 40. A secondary winding 62b is connected between the gate and cathode of silicon controlled rectifier 56 to apply turn-on gate pulses thereto rapidly to render the silicon controlled rectifier highly conductive to discharge capacitor 52 into the primary winding 14a in synchronism with the opening of the breaker-point assembly 40.

Upon closing of the mechanical breaker-point assembly 40, current will flow from the positive potential at terminal 24 through the resistor 64 and the primary winding 62a of the pulse forming transformer 62. However, this initial current flow produces a negative potential at the secondary winding 62b and, as such, has no affect on the silicon controlled rectifier 56. However, upon subsequent opening of the mechanical breaker-point assembly 40 current flow through the primary winding 62a is abruptly terminated and the magnetic field within the transformer 62 rapidly collapses to produce a positive polarity pulse within the secondary winding 62b to trigger the silicon controlled rectifier 56 to its highly conductive state. This action, as mentioned hereinabove, rapidly discharges capacitor 52 through the primary winding 14a of the ignition coil 14 to generate a high voltage spark at the output thereof. A diode 66 is connected across the primary winding 62a substantially to reduce and dampen the reverse kick-back voltages which may occur within the pulse forming transformer 62.

Connected in parallel with primary winding 14a of the ignition coil 14 is a diode 68 and a bi-directional threshold switching device 70, or any other suitable voltage dependent resistance means, which serves to prevent voltage break-down of the diode 68 which, in turn, serves to rectify oscillations in the primary winding 14a after the high voltage spark discharge has been created at the output of the secondary winding 14b.

If desired, a triggering amplifier may be used with the single swing blocking oscillator formed by transistor 42 and transformer 44 to apply the necessary re-initiation pulse to the transistor 42 for the next cycle of operation which will apply another energy pulse to capacitor 52. The triggering amplifier is herein illustrated as including a transistor 72 forming an emitter-follower circuit with a resistor 74 connected to the emitter electrode thereof and to the circuit point 28 for receiving an operating potential. The output of transistor 72 is coupled to the base electrode of transistor 42 through a coupling capacitor 76. The base electrode of transistor 72 is connected to one end of the capacitor 52 and secondary winding 44c through a resistor 78 and a diode 80. When the silicon controlled rectifier 56 is rendered conductive to discharge capacitor 52 into the primary winding 14a, .the potential across capacitor 52 and across the secondary winding 44c rapidly decreases substantially to zero. Thus, at this point in time a slight ringing current is generated between the capacitor 52 and secondary winding 44c so that a short duration negative potential is sensed at the cathode of diode 80 to forward bias the diode which, in turn, renders triggering transistor 72 conductive. This negative potential which is applied to the cathode of diode 80 also serves to commutate the silicon controlled rectifier 56 to an off condition immediately after discharge of capacitor 52. When transistor 72 is rendered conductive a negative pulse is applied through capacitor 76 to the base electrode of transistor 42. This negative pulse reverse biases the transistor 42 and the transistor remains in its non-conductive state. However, shortly thereafter the potential at diode 80 rapidly changes from zero to a positive potential to reverse bias the diode 80 and render transistor 72 non-conductive. This action will produce a positive pulse through capacitor 76 which, in turn, will initiate operation of transistor 42 to deliver another energy pulse to the capacitor 52. It will be noted that a slight delay exists between the time capacitor 52 is discharged and the time transistor 42 is rendered conductive to apply another energy pulse to the capacitor 52.

A pair of series connected diodes 82 and 84 are connected between the base and emitter electrodes of transistor 42 and serves as reference potential means to limit the forward voltage drop between the base and emitter of transistor 42 to prevent damage thereto during normal operating conditions. Also, a diode 86 has its anode connected to the emitter electrode of transistor 42 and its cathode connected to the base electrode of transistor 42. During the collapse of the magnetic field within the transformer 44, and substantially immediately thereafter, the diode 86 is forward biased to dampen any tendencies of sustained oscillation within the blocking oscillator circuit and provides back swing limiting in such a fashion that the repetition rate and duty cycle of the single swing blocking oscillator are not materially affected.

The illustrated embodiment of the energy pulsing circuit 12 receives its operating voltage from the battery 20 through the power switching circuit 16 which is constructed in accordance with the principles of-this invention. It will be noted that at all times, voltage is applied to circuit point 18 of the power switching circuit 16 but no voltage is applied to circuit point 28 until the ignition switch 22 is closed, which in turn, energizes a power switching current control device, here being illustrated as a silicon controlled rectifier 90. In the case of a negative ground system, the anode of silicon controlled rectifier 90 is connected to circuit point 18 while the cathode thereof is connected to circuit point 28 to form a series power switch selectively to apply power from circuit point 18 to circuit point 28 only under normal voltage conditions. The gate electrode of silicon controlled rectifier 90 is connected through a diode 92 and resistor 94 to the ignition switch 22 as defined by circuit point 24. Upon closing the ignition switch 22 a control current will flow through the gate cathode circuit of silicon controlled rectifier 90 thereby rendering it conductive to apply operating potential to the energy pulsing circuit 12. A disabling transistor 96 has its load electrodes, i.e., the collector and emitter thereof, connected between the gate electrode of silicon controlled rectifier 90 and ground potential. When transistor 96 is rendered highly conductive, which will occur only during an abnormal voltage condition, the control current which would otherwise be delivered to the gate cathode circuit of silicon controlled rectifier 90 is shunted to ground thereby disabling the silicon controlled rectifier 90. The base electrode of transistor 96 is connected to circuit point 18 via a resistor 98, a diode 100, a resistor 102, and a threshold voltage switching device 104. The threshold voltage switching device 104 is herein illustrated as a zener diode, but it will be understood that any suitable threshold voltage device can be used. Also, it will be understood that any circuit coupling arrangement can be made between the base electrode of transistor 96 and circuit point 18 other than the specific arrangement shown.

If for some reason, an overvoltage occurs at circuit point 18, as by a loose or disconnected terminal of battery 20 while the alternator 30 is producing an output voltage in the order of 30 volts or more, the threshold switching device 104 will breakover to apply a forward bias potential at the base electrode of transistor 96 to render it highly conductive and shunt the gate cathode circuit of silicon controlled rectifier 90 thereby disabling the silicon controlled rectifier. The threshold voltage value of the threshold switching device 104 is selected to cause disabling of silicon controlled rectifier 90 upon sensing of an abnormal voltage in excess of, for example, 25 volts or more, thus preventing high potentials from being applied to the energy pulsing circuit 12 to protect the circuit.

Connected in parallel with the threshold voltage device 104 are the load electrodes of a transistor 106 which is maintained in its non-conductive condition while normal operating voltages are sensed between circuit points 18 and 24. The base electrode of transistor 106 is connected through a resistor 108 to the circuit point 24. When switch 22 is closed the voltage value between circuit points 18 and 24 are the same, or substantially the same, and no forward bias condition exists between the base emitter electrodes of the transistor 106 and this transistor is maintained in its nonconductive condition. However, on opening of the ignition switch 22 a reduced voltage is sensed at circuit point 24, this voltage being the residual feedback voltage of the alternator 30 or, in the case where no residual feedback voltage occurs, a zero voltage condition.

The base emitter junction of transistor 104 is then forward biased by means of the positive potential at circuit point 18 and the reduced or zero potential at circuit point 24 to render the transistor 106 conductive which, in turn, applies a forward bias potential to transistor 96 rendering it conductive. The conduction of 96 by means of transistor 106 also shunts the control current which would otherwise be applied to the gate electrode of silicon controlled rectifier to ground potential, thus disabling the silicon controlled rectifier 90 upon sensing a voltage difference between the circuit points 18 and 24. Therefore, an abnormal voltage condition of either an overvoltage applied to circuit point 18 or a voltage differential between circuit points 18 and 24 will cause automatic and instantaneous deenergization of silicon control rectifier 90 to remove power from circuit point 28 and disable and protect the energy pulsing circuit 12.

A bias filter capacitor 109 is connected between the emitter and base electrodes of transistor 96 to maintain the transistor in a stable conducting condition when an abnormal voltage condition is sensed, so as to maintain the silicon controlled rectifier 90 in an off condition. Also, a filter capacitor 110 is connected between the emitter electrode of transistor 96 and the circuit point 28 and may serve to commutate the silicon controlled rectifier 90 to an off condition, which off condition is maintained so long as the control current to the gate electrode thereof is shunted to ground potential by transistor 96.

Accordingly, the power switching circuit 16 of this invention provides means for sensing abnormal voltage conditions of either an overvoltage to protect the energy pulsing circuit 12 connected thereto and to sense an abnormal voltage condition of a voltage differential between the supply voltage as applied to one input of the power switching circuit 16 and a residual feedback voltage which exists at the ignition switch and which is applied to the other input of the power switching circuit 16. The power switching circuit 16 therefore functions as an electronic relay to apply operating potentials to the energy pulsing circuit 12 only under normal voltage conditions.

We claim:

1. An ignition system for applying a spark producing voltage to a primary winding of an ignition coil to generate a spark discharge between spaced-apart electrodes associated with the secondary winding thereof,

in synchronization with external pulse signal information, comprising:

storage means for receiving and storing electrical energy; an energy pulsing circuit coupled to said storage means to apply a pulse of energy to said storage means after a previous pulse of energy has been dissipated therefrom, said energy pulsing circuit having a trigger circuit portion arranged for connection to an external power source through a switch; said trigger circuit portion being responsive to the external pulse signal information; power switching circuit means including a current control device having load electrodes and a control electrode, one of said load electrodes connected to said energy pulsing circuit and another of said load electrodes arranged for direct connection to the external power source through a first circuit point;

and voltage abnormality sensing means coupled to said control electrode and arranged for connection to said switch on the side thereof connected to said circuit portion of said energy pulsing circuit, said current control device being rendered highly conductive when the voltage value of the external power source is below a predetermined value and is substantially equal to the voltage value applied to said circuit portion through said switch for applying power to said energy pulsing circuit, said current control device being rendered non-conductive to a current blocking condition in response to said voltage abnormality sensing means when the voltage value of the external power source exceeds said predetermined value and when the voltage value of the external power source and the voltage value on said switch at the side thereof connected to said circuit portion are different, to remove power completely from said energy pulsing circuit.

2. The ignition system of claim 1 wherein said energy pulsing circuit includes a capacitor, means for applying a high voltage energy pulse to said capacitor, and switching means responsive to the external pulse signal information to discharge said capacitor through the ignition coil to generate a spark discharge at the output thereof.

3. The ignition system of claim l wherein said first current control device is a silicon controlled rectifier having its anode cathode electrodes connected be tween said first circuit point and said energy pulsing circuit, and its gate electrode coupled to said voltage abnormality sensing means, said voltage abnormality sensing means including a first transistor having the collector emitter electrodes thereof connected between the gate electrode of said silicon controlled rectifier and the ground potential and the base electrode thereof coupled to the juncture of a threshold voltage switch device and the output terminal of a second transistor which is arranged for sensing the difference between the voltage value of the external power source and the voltage value on said switch at the side thereof connected to said circuit portion, said second transistor having a first input electrode connected to said first circuit point and a second input electrode connected to a second circuit point, whereby an increase in voltage at said first circuit point beyond said predetermined voltage value will render said threshold voltage switching device conductive to render said first transistor conductive which, in turn, will render said silicon controlled rectifier non-conductive to remove power from said energy pulsing circuit, and a decrease in voltage value at said second circuit point below that at said first circuit point will provide an output signal at the output terminal of said second transistor also to render said first transistor conductive which, in turn, will render said silicon controlled rectifier non-conductive to remove power from said energy pulsing circuit.

4. An ignition system for applying a spark producing voltage to a primary winding of an ignition coil to generate a spark discharge between spaced-apart electrodes associated with the secondary winding thereof in synchronization with external pulse signal information, comprising:

storage means for receiving and storing electrical energy;

an energy pulsing circuit coupled to said storage means to apply a pulse of energy to said storage means after a previous pulse of energy has been dissipated therefrom, said energy pulsing circuit having a trigger circuit portion arranged for connection to an external power source through a switch, said trigger circuit portion being responsive to the external pulse signal information;

power switching means including a current control device having load electrodes and a control electrode, one of said load electrodes connected to said energy pulsing circuit and another of said load electrodes arranged for direct connection to the external power source through a first circuit point, and

overvoltage sensing means coupled to said control electrode of said current control device and arranged for connection to said switch on the side thereof connected to said trigger circuit portion of said energy pulsing circuit, said current control device being rendered non-conductive to a current blocking condition in response to said overvoltage sensing means when the voltage value of the external power source exceeds said predetermined voltage to remove power completely from said energy pulsing circuit.

5. The ignition system of claim 4 including voltage differential sensing means coupled to said control elec trode of said current control device and arranged for connection to said switch on the side thereof connected to said circuit portion of said energy pulsing circuit, said voltage differential sensing means effecting nonconduction of said current control device when the voltage value of the external power source and the voltage value on said switch at the side thereof connected to said circuit portion are different, to remove power completely from said energy pulsing circuit.

6. The ignition system of claim 4 wherein said overvoltage sensing means includes a threshold voltage device connected in circuit with said control electrode of said current control device to cause bypassing of control current which would be applied thereto when an overvoltage condition is sensed.

7. In a capacitor discharge ignition system for an internal combustion engine having a trigger circuit connected to a power supply through an ignition switch which trigger circuit is operative to discharge the ignition capacitor in a timed relation to engine RPM, the ignition system further including an ignition capacitor charging circuit for charging the ignition capacitor subsequent to the discharge thereof by the trigger circuit, the combination including, a protective circuit for reducing damage to the ignition system components due to an abnormal increase of the power supply voltage, said protective circuit comprising an electron switch connected between the power supply and the ignition capacitor charging circuit, said electron switch having a control circuit connected to the power supply with the ignition switch being closed, said control circuit being responsive to a normal power supply voltage to render said electron switch conductive to couple a potential from the power supply through said electron switch to the capacitor charging circuit thereby rendering the ignition system operable, said control circuit further being responsive to the voltage of the power supply increasing to a predetermined abnormal level to render said electron switch nonconductive thereby removing the power supply potential from the capacitor charging circuit making the ignition system inoperable and protecting the electronic components thereof.

8. The capacitor discharge ignition system of claim 7 wherein the power supply includes a battery, an alternator and connecting means connecting the battery to the alternator with the engine operating for charging the same, said connecting means further preventing the battery from discharging through the alternator with the ignition switch open, and wherein the trigger circuit and alternator output on the alternator side of the connecting means are connected to a first circuit portion of said control circuit of said electron switch, and with the ignition switch being open the battery of the power supply is connected to a second circuit portion of said control circuit, said control circuit further having electron control means connected to said first and second circuit portions and being responsive to both the residual feedback voltage generated by the alternator and coupled therefrom to said first circuit portion and to the battery potential coupled to said second circuit portion thereof with the ignition switch being opened to render said electron switch nonconductive thereby preventing the residual feedback voltage from the alternator from operating the ignition system.

9. The capacitor discharge ignition system of claim 8 wherein said electron control means includes first and second semiconductor devices each having input, output and control electrodes, and said electron switch is a silicon controlled rectifier having an input electrode connected to the power supply on the battery side of the connecting means, an output electrode connected to the capacitor charging circuit and a gate electrode connected to the alternator output on the alternator side of the connecting means and to the battery through the ignition switch, said first semiconductor switch having its input electrode connected to the battery, its control electrode connected to the alternator output on the alternator side of the connecting means and its output electrode connected to the control electrode of said second semiconductor device, said second semiconductor device further having its input electrode connected to the alternator output on the alternator side of the connecting means and the gate electrode of said silicon controlled rectifier and its output electrode connected to a reference potential whereby with the opening of the ignition switch the potential difference between the battery voltage on the input electrode of said first semiconductor switch and the alternator residual feedback voltage on the control electrode thereof energizes said first semiconductor device thereby energizing said second semiconductor device to shunt the alternator residual feedback voltage therethrough from the gate electrode of said silicon controlled rectifier to said reference potential to positively disenable the ignition system.

10. The ignition system of claim 7 wherein said electron switch is a silicon controlled rectifier having its anode and cathode electrodes connected between the power supply and the ignition capacitor charging circuit and its gate electrode coupled by said control circuit through said ignition switch to the power supply with the switch being closed for receiving a control current to render the silicon controlled rectifier conductive, and said control circuit having electron control means connected to said gate electrode of said silicon controlled rectifier and being responsive to a predetermined abnormal level of the power supply potential for shunting said control current from said gate electrode of said silicon controlled rectifier thereby causing said silicon controlled rectifier to be rendered nonconductive to remove power from the ignition capacitor charging circuit.

11. The ignition system of claim 10 wherein said electron control means includes a semiconductor device having first and second load electrodes and a control electrode, said control electrode arranged for receiving an operating current indicative of an abnormal voltage condition of the power supply and one of said load electrodes thereof connected to the gate electrode of said silicon controlled rectifier and the other to a reference potential, said semiconductor device being energized by said operating current to shunt said control current therethrough from said gate electrode of said silicon controlled rectifier thereby rendering said silicon controlled rectifier non-conductive to remove power from the capacitor charging circuit.

12. The ignition system of claim 11 wherein said control circuit further includes a threshold voltage switching device having one electrode thereof connected to the control electrode of said semiconductor device and another electrode thereof connected to the power supply, said threshold voltage switching device being rendered conductive upon sensing an increase in voltage of the power supply to said predetermined abnormal voltage level to render said semiconductor device conductive which, in turn, renders said silicon controlled rectifier non-conductive to remove power from the capacitor charging circuit.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 828,750

DATED I August 13, 1974 INVENTOR(S) i Gunter G. Schuette .W' liam J. Warner It rs certlfred tht error appears rn the above-rdentrfred patent and that sard Letters Patent are hereby corrected as shown below:

Col. 3, line 67 change "useful" to used.

Col. 6 line 60 after "slight" insert time--.

Col. 9, line 57 change "switch" to --sWitching--.

Signed and sealed this 6th day of May 1975.

(SEAL) Attest:

v C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. An ignition system for applying a spark producing voltage to a primary winding of an ignition coil to generate a spark discharge between spaced-apart electrodes associated with the secondary winding thereof, in synchronization with external pulse signal information, comprising: storage means for receiving and storing electrical energy; an energy pulsing circuit coupled to said storage means to apply a pulse of energy to said storage means after a previous pulse of energy has been dissipated therefrom, said energy pulsing circuit having a trigger circuit portion arranged for connection to an external power source through a switch; said trigger circuit portion being responsive to the external pulse signal information; power switching circuit means including a current control device having load electrodes and a control electrode, one of said load electrodes connected to said energy pulsing circuit and another of said load electrodes arranged for direct connection to the external power source through a first circuit point; and voltage abnormality sensing means coupled to said control electrode and arranged for connection to said switch on the side thereof connected to said circuit portion of said energy pulsing circuit, said current control device being rendered highly conductive when the voltage value of the external power source is below a predetermined value and is substantially equal to the voltage value applied to said circuit portion through said switch for applying power to said energy pulsing circuit, said current control device being rendered nonconductive to a current blocking condition in response to said voltage abnormality sensing means when the voltage value of the external power source exceeds said predetermined value and when the voltage value of the external power source and the voltage value on said switch at the side thereof connected to said circuit portion are different, to remove power completely from said energy pulsing circuit.
 2. The ignition system of claim 1 wherein said energy pulsing circuit includes a capacitor, means for applying a high voltage energy pulse to said capacitor, and switching means responsive to the external pulse signal information to discharge said capacitor through the ignition coil to generate a spark discharge at the output thereof.
 3. The ignition system of claim 1 wherein said first current control device is a silicon controlled rectifier having its anode cathode electrodes connected between said first circuit point and said energy pulsing circuit, and its gate electrode coupled to said voltage abnormality sensing means, said voltage abnormality sensing means including a first transistor having the collector emitter electrodes thereof connected between the gate electrode of said silicon controlled rectifier and the ground potential and the base electrode thereof coupled to the juncture of a threshold voltage switch device and the output terminal of a second transistor which is arranged for sensing the difFerence between the voltage value of the external power source and the voltage value on said switch at the side thereof connected to said circuit portion, said second transistor having a first input electrode connected to said first circuit point and a second input electrode connected to a second circuit point, whereby an increase in voltage at said first circuit point beyond said predetermined voltage value will render said threshold voltage switching device conductive to render said first transistor conductive which, in turn, will render said silicon controlled rectifier non-conductive to remove power from said energy pulsing circuit, and a decrease in voltage value at said second circuit point below that at said first circuit point will provide an output signal at the output terminal of said second transistor also to render said first transistor conductive which, in turn, will render said silicon controlled rectifier non-conductive to remove power from said energy pulsing circuit.
 4. An ignition system for applying a spark producing voltage to a primary winding of an ignition coil to generate a spark discharge between spaced-apart electrodes associated with the secondary winding thereof in synchronization with external pulse signal information, comprising: storage means for receiving and storing electrical energy; an energy pulsing circuit coupled to said storage means to apply a pulse of energy to said storage means after a previous pulse of energy has been dissipated therefrom, said energy pulsing circuit having a trigger circuit portion arranged for connection to an external power source through a switch, said trigger circuit portion being responsive to the external pulse signal information; power switching means including a current control device having load electrodes and a control electrode, one of said load electrodes connected to said energy pulsing circuit and another of said load electrodes arranged for direct connection to the external power source through a first circuit point, and overvoltage sensing means coupled to said control electrode of said current control device and arranged for connection to said switch on the side thereof connected to said trigger circuit portion of said energy pulsing circuit, said current control device being rendered non-conductive to a current blocking condition in response to said overvoltage sensing means when the voltage value of the external power source exceeds said predetermined voltage to remove power completely from said energy pulsing circuit.
 5. The ignition system of claim 4 including voltage differential sensing means coupled to said control electrode of said current control device and arranged for connection to said switch on the side thereof connected to said circuit portion of said energy pulsing circuit, said voltage differential sensing means effecting non-conduction of said current control device when the voltage value of the external power source and the voltage value on said switch at the side thereof connected to said circuit portion are different, to remove power completely from said energy pulsing circuit.
 6. The ignition system of claim 4 wherein said overvoltage sensing means includes a threshold voltage device connected in circuit with said control electrode of said current control device to cause bypassing of control current which would be applied thereto when an overvoltage condition is sensed.
 7. In a capacitor discharge ignition system for an internal combustion engine having a trigger circuit connected to a power supply through an ignition switch which trigger circuit is operative to discharge the ignition capacitor in a timed relation to engine RPM, the ignition system further including an ignition capacitor charging circuit for charging the ignition capacitor subsequent to the discharge thereof by the trigger circuit, the combination including, a protective circuit for reducing damage to the ignition system components due to an abnormal increase of the power suppLy voltage, said protective circuit comprising an electron switch connected between the power supply and the ignition capacitor charging circuit, said electron switch having a control circuit connected to the power supply with the ignition switch being closed, said control circuit being responsive to a normal power supply voltage to render said electron switch conductive to couple a potential from the power supply through said electron switch to the capacitor charging circuit thereby rendering the ignition system operable, said control circuit further being responsive to the voltage of the power supply increasing to a predetermined abnormal level to render said electron switch nonconductive thereby removing the power supply potential from the capacitor charging circuit making the ignition system inoperable and protecting the electronic components thereof.
 8. The capacitor discharge ignition system of claim 7 wherein the power supply includes a battery, an alternator and connecting means connecting the battery to the alternator with the engine operating for charging the same, said connecting means further preventing the battery from discharging through the alternator with the ignition switch open, and wherein the trigger circuit and alternator output on the alternator side of the connecting means are connected to a first circuit portion of said control circuit of said electron switch, and with the ignition switch being open the battery of the power supply is connected to a second circuit portion of said control circuit, said control circuit further having electron control means connected to said first and second circuit portions and being responsive to both the residual feedback voltage generated by the alternator and coupled therefrom to said first circuit portion and to the battery potential coupled to said second circuit portion thereof with the ignition switch being opened to render said electron switch nonconductive thereby preventing the residual feedback voltage from the alternator from operating the ignition system.
 9. The capacitor discharge ignition system of claim 8 wherein said electron control means includes first and second semiconductor devices each having input, output and control electrodes, and said electron switch is a silicon controlled rectifier having an input electrode connected to the power supply on the battery side of the connecting means, an output electrode connected to the capacitor charging circuit and a gate electrode connected to the alternator output on the alternator side of the connecting means and to the battery through the ignition switch, said first semiconductor switch having its input electrode connected to the battery, its control electrode connected to the alternator output on the alternator side of the connecting means and its output electrode connected to the control electrode of said second semiconductor device, said second semiconductor device further having its input electrode connected to the alternator output on the alternator side of the connecting means and the gate electrode of said silicon controlled rectifier and its output electrode connected to a reference potential whereby with the opening of the ignition switch the potential difference between the battery voltage on the input electrode of said first semiconductor switch and the alternator residual feedback voltage on the control electrode thereof energizes said first semiconductor device thereby energizing said second semiconductor device to shunt the alternator residual feedback voltage therethrough from the gate electrode of said silicon controlled rectifier to said reference potential to positively disenable the ignition system.
 10. The ignition system of claim 7 wherein said electron switch is a silicon controlled rectifier having its anode and cathode electrodes connected between the power supply and the ignition capacitor charging circuit and its gate electrode coupled by said control circuit through said ignition switch to the power supply with the switCh being closed for receiving a control current to render the silicon controlled rectifier conductive, and said control circuit having electron control means connected to said gate electrode of said silicon controlled rectifier and being responsive to a predetermined abnormal level of the power supply potential for shunting said control current from said gate electrode of said silicon controlled rectifier thereby causing said silicon controlled rectifier to be rendered non-conductive to remove power from the ignition capacitor charging circuit.
 11. The ignition system of claim 10 wherein said electron control means includes a semiconductor device having first and second load electrodes and a control electrode, said control electrode arranged for receiving an operating current indicative of an abnormal voltage condition of the power supply and one of said load electrodes thereof connected to the gate electrode of said silicon controlled rectifier and the other to a reference potential, said semiconductor device being energized by said operating current to shunt said control current therethrough from said gate electrode of said silicon controlled rectifier thereby rendering said silicon controlled rectifier non-conductive to remove power from the capacitor charging circuit.
 12. The ignition system of claim 11 wherein said control circuit further includes a threshold voltage switching device having one electrode thereof connected to the control electrode of said semiconductor device and another electrode thereof connected to the power supply, said threshold voltage switching device being rendered conductive upon sensing an increase in voltage of the power supply to said predetermined abnormal voltage level to render said semiconductor device conductive which, in turn, renders said silicon controlled rectifier non-conductive to remove power from the capacitor charging circuit. 